The average gasoline price of one of the major oil companies has been $3.00 per gallon. Because of shortages in production of crude oil, it is believed that there has been a significant increase in the average price. In order to test this belief, we randomly selected a sample of 36 of the company's gas stations and determined that the average price for the stations in the sample was $3.20. Assuming that the standard deviation of the population is $0.22, test the hypothesis that gas prices have increased at the 5% significance level.